This invention relates to apparatus for improving the safety of a portable chain saw; and in particular, to an improved apparatus for braking the chain saw in the event of an unexpected or uncontrollable hazardous movement, to which chain saws can be subject.
It is well known that portable chain saws are subject to a potentially hazardous kick-back motion during operation, and that a chain brake can be provided to reduce the risk of operator injury in the event of a kick-back resulting in an untoward saw movement. The present state of the art has tended toward a less complicated and complex safety brake construction in which a safety brake handle is provided forward of a gripping handle, so that during kick-back, the operator's hand or arm will force the safety brake handle forward thereby applying a braking force to the chain saw motor. Such systems are applicable to both electrically powered and gasoline powered chain saws. While these newer systems often reduce the complexity of the mechanism, they can also tend to provide additional wear and less mechanical flexibility since a single spring is employed to perform the two tasks of resiliently restraining the safety brake handle and biasing the handle to the forward position. This dual requirement provides off-center forces which cause uneven wear on the latch and release mechanism components. Notwithstanding therefore the significant advancements in the art of safety brakes for chain saws, there still is room for further improvement.
Accordingly, therefore, it is an object of this invention to provide an improved chain braking structure for a portable chain saw. Other objects of the invention are to provide a safety brake mechanism for a chain saw having improved reliability, low manufacturing costs, greater flexibility, and applicability to both electric and gasoline powered chain saws.